In the field of the art of dentistry and dental craft, partial dentures are well known dental fixtures used in replacement of one and more often more lost teeth, being supported by available teeth and mounted onto the alveolar ridge. By replacing lost teeth, partial dentures aim at restoration of the partially lost function of mastication and speech, at preserving and improving the health of soft mouth tissues, at effecting an aesthetic appearance and at improving the overall health of the user.
Typically, a partial denture comprises the base or bases, major and minor connectors, direct and indirect retaining means and a plurality of artificial teeth. Whatever, the category of classification or partial dentures, i.e. whether the partial denture aims at filling with teeth an edentulous area on a single mouth side or on either side thereof, partial dentures need to be adequately supported, retained and stabilized, both horizontally and vertically, against forces applied during mastication or weight forces or forces due to adhesion of food or to stresses arising during speech, cough, laugh, etc. Partial denture supporting, retaining and stabilizing is thereby effected by means of connectors, such as the broadly used palatal bars extending all the way through from one end to the other end of the oral cavity. These connectors are obviously not comfortable for the user. However, the state of the art of partial dentures has not provided a solution to the aforementioned problem and even in the case of a single-sided partial denture such connecting means have to extend all the way through the oral cavity from one side to the other to adequately support the partial denture.
It is therefore the first main object of the present invention to provide an alternative method of supporting a partial denture with unilateral anchorage and thereby eliminate the undesirable, uncomfortable connecting means, which in accordance with prior art method and techniques necessarily extend all the way through, from one side to the other side of the oral cavity.
Satisfying of the above main object of the invention, brings forward the object to provide a new type of precision attachment, classified within the general category of direct retaining means of the prior art, but with substantial advantages over the latter, as will become apparent herein after.
Direct retaining means of the prior art are those parts of the partial denture, which are applied in a certain manner, intracoronal or extracoronal, upon the supporting teeth and retain the partial denture thereon.
Precision attachments are a special type of direct retaining means and comprise a female portion which is retained in an inlay within the anatomical crown or is embodied within an artificial golden crown and a male portion which is mounted onto the base of the partial denture, wherein insertion of the partial denture and retaining of the same is effected by interconnection of the male and female portions of the precision attachment.
Retention capacity of such a precision attachment is dependent upon frictional forces between aforementioned male and female portions, these forces exerting, according to the design of the attachment, suitable, required resistance to the displacement forces exerted onto the partial denture. However, such attachments of the prior art are fixedly connected to the base of the partial denture, such inflexible connection not allowing any movement of the attachment independently of the base of the partial denture.
Aiming at reduction of forces exerted during mastication onto supporting teeth of the partial denture and at a more even distribution of stresses exerted by the denture onto soft mouth tissues, as well as at inhibiting undesired twisting or inclining of teeth of the partial denture, attachments have been designed which are flexibly connected to the base of the partial denture, thereby performing a strain absorbing activity, i.e. acting so as to reduce stresses applied onto the supporting teeth. A broad variety of such precision attachments has been developed and is commercially available. Precision attachments amongst this variety differ with respect to the extent of allowance of movement of the direct retaining means with respect to the base of the partial denture.
Precision attachments of the prior art incorporating such a strain absorbing activity are often complicated accessories with a movable male portion consisting of a plurality of parts which increase cost of the attachment and require a substantially high accuracy for their assembling. Furthermore, none of the precision attachments of the prior art can offer the ability of unilateral anchorage of a partial denture, since construction of these attachments is such that, if the attachment were to be used without retaining means on the other side, it would allow freedom of movement in at least two directions, i.e. displacement of the male relatively to the female portion, namely freedom of rotation of the male within the female portion, such rotation resulting to sideways displacement of the entire partial denture. Moreover, connection of the male and female portions in precision attachments of the prior art--if without retaining means on the other side of the oral cavity--would cause increased stresses because of the forces developing during mastication or related forces due to muscular stresses (cough, laugh, etc.). Thus, precision attachments of the prior art, either those with strain absorbing capacity or those without, require supporting of the partial denture via retaining means at the other side of the oral cavity, which result to the undesired, uncomfortable to feel provision of connectors, such as palatal bars extending all the way along the oral cavity, from one side to the other.
It is therefore an object of the present invention to effectively overcome disadvantages and drawbacks of the prior art and provide a precision attachment for a partial denture with unidirectional freedom of movement, which ensures adequate supporting of the partial denture with unilateral anchorage, thereby eliminating the undesired connecting elements of the prior art, this precision attachment further incorporating a strain absorber capacity, allowing such movements of the partial denture which contribute towards eliminating stresses due to forces developing during mastication and entirely inhibiting sideways movement of the partial denture, which is the decisive factor forcing prior art to employ retaining means on either side of the oral cavity.
Because of the necessity of retaining means on either side of the oral cavity for partial dentures of the prior art, making such partial dentures, irrespective of the type of retaining means (connectors or clasps), requires a substantial fine quality work of the dentist in cooperation with the dental technician and many repetitive visits of the patient to the dentist. Partial dentures of the prior art further require more teeth of the patient to be employed in a supporting role. Obviously, the above substantially increase the cost of the partial denture.
Furthermore, when the need arises for maintenance, repair and partial replacement work of the partial denture and in particular if the precision attachment employed in connection thereto needs to be replaced, the patient has again to undergo repetitive, uncomfortable and costly visits to the dentist for repairing the damage. In this respect it is well known that conventional connectors of the prior art are often apt to wear and loss of their retaining capacity due to frictional contact of male and female portions thereof.
It is therefore a further object of the present invention to disclose such a manner of interconnecting parts of the proposed precision attachment on the one side onto supporting tooth and on the other side onto the partial denture, so that maintenance or even replacement due to wear of the attachment may be made possible without the repetitive, costly and uncomfortable visits of the patient to the dentist for restoring the damage.
It is further well known and obvious that partial dentures of the prior art with the multiple connecting elements and retaining means are complex structures and because of that necessitate following a strictly defined insertion path with a plurality of supporting points and thus it is difficult for the user to insert the partial denture, especially when he is old aged and lacks the ability of performing the highly accurate movements required. Thus, it is often noted that required periodical cleaning and maintenance of the partial denture is not done in accordance with requirements.
It is therefore an object of the present invention to provide a partial denture equipped with the precision attachment of the invention, which has a strain absorber capacity the partial denture being thereby supported with unilateral anchorage, the sole means of anchorage thereof being the proposed precision attachment, the partial denture being easily detachable and easily reinserted into the user's mouth, since it does not require following a strictly defined insertion path, but requires locating a single supporting point only.
These and other objects, characteristics and merits of the present invention will be made apparent in the detailed description following hereinafter.